Compared to those with the lowest quartile (Q1) of plasma insulin or C-peptide levels, levels of these analytes in the fourth quartile (Q4) were associated with a 2 to 5-fold increased risk of adenomas (OR = 3.5, 95% CI 1.7-7.4, p-trend = 0.002, OR = 2.2, 95% CI 1.2-4.0, p-trend = 0.04, respectively). This evidence concerns the gene INS and adenoma.